I agree, I don't see how you would have trouble with Metroid when you have played so much Resident Evil.
What I would suggest instead of playing the 3D metroids however is going back and playing the 2D Metroids. They are not only a little easier, but much faster and 'common sense' gameplay. Much like Zelda. Which its understandable you said you haven't finished a Zelda either, but it seems you started right away with the later 3D Zeldas which may follow the same trend of what I'm talking about.
I would suggest starting with Metroid: Zero Mission, then Metroid II, then Super Metroid then Metroid Fusion. Basically, the 2D games in chronological order. Not only will it prepare you for Metroid: Other M storywise, but it'll introduce you back into Metroid gradually difficultywise. The 3D Metroid games are still great, but they don't tie into the main Metroid storyline Metroid: Other M is going to go into and they're a lot more confusing to play (a ton of backtracking, harder bosses, etc).
As for Zelda, you should also play that someday. I'd suggest a similar formula for playing those games. Start with the earlier games and work your way up. Only game you might have a problem with is Zelda II.
Six upcoming games you should look into:
